The present invention relates to a method for controlling a brake system, in particular for controlling a regenerative brake system with a number of friction brakes and an electro-regenerative brake.
It is the purpose of regenerative brake systems in motor vehicles to store at least part of the energy produced during braking in the motor vehicle and to re-use it for the drive of the vehicle. This provision allows reducing the energy consumption of the vehicle in total, increasing the efficiency, and thus rendering its operation more economical. To this effect, motor vehicles with a regenerative brake system generally include different types of brakes, also called brake actuators.
Typically, this arrangement employs a number of hydraulic friction brakes, as known from customary motor vehicles, and an electro-regenerative brake. The electro-regenerative brake is generally configured as an electric generator, generating at least part of the total brake output. The produced electric energy is supplied into a storage medium such as an on-board battery, or is fed back, respectively, and is re-used for driving the motor vehicle by way of an appropriate drive.
Regenerative brake systems can be designed as so-called serial regenerative concepts where the component of the brake torque, which is produced by the generator, is as high as possible. In contrast thereto, parallel or so-called residual-moment-based regenerative concepts are known as well, where the brake torque is distributed in predefined ratios to the brake actuators or to individual brakes, e.g. axlewise. Mixed concepts of these two brake concepts are likewise known. It is common to all systems that they use several different brakes for simultaneous braking at least in some ranges of the brake torque to be generated so that the total deceleration is composed of the deceleration components of the mentioned brakes.
The problem involved in regenerative bake systems is that when using different brake actuators, the systems can generate effective brake forces that differ from each other in spite of equal brake force requirements. This becomes noticeable in a negative way especially when shifting the brake requirements from one brake actuator to the other one, if the deceleration components of the brake actuators differ from a defined ratio. To balance these shortcomings, it is possible to apply a static correction factor to one or more of the brake actuators. However, it is not possible to eliminate the drawbacks thereby to full extent because the performance of the brake actuators is related to the vehicle, as e.g. the brake linings can be different due to series deviation during production. In addition, the attainable deceleration values of the brake actuators, such as of the hydraulic friction brake in particular, can vary due to wear and aging. A static correction factor can neither take any influence when exchanging brake elements that wear off, such as brake linings and brake discs, as customary in motor vehicles.
In view of the above, an object of the invention is to disclose a method for controlling a brake system as described hereinabove, wherein the actual deceleration components of the brakes of the total deceleration correspond to the nominal deceleration components as exactly as possible.